Apparatus for recovering glycerin



Oct. l5, 1940. B CLAYTON APPARATUS FOR RECOVERING GLYCERIN origial FiledNov. s, 1937 2 sheets-sheen` 1 rmentor' fy'amz'z (Zayfa/z gm 7L Gtfomggsoct. 15, 194,0.,v B, CLAYTON 2,218,279

APPARATUS FOR RECOVERING GLYCERIN Driginal Filed Nov. 3, 1937 i 2Sheets-Sheet 2 :inventor e/J'a/mh [Zayffz M f Gttornegs Patented Oct.15, 1940 UNITED STATES APPARATUS FOR RECOVERING G LYCERIN BenjaminClayton, Houston, Tex., assignor to Refining, Inc., Reno, Nev., a.corporation of Nevada Original application November 3, 1937, Serial No.172,644. Divided and this application April 11,

1938, Serial No. 201,443

1 Claim..

This-invention relates to a process and apparatus for recoveringglycerin and more particularly to a process and apparatus for recoveringglycerin'from admixture with soap'.

In the production of soap from fats and oils containing glycerin incombination, relatively large proportions of glycerin are produced andthis glycerin constitutes a valuable by-product. The conventionalprocess of separating and recovering the glycerin from the soap mixturesis by adding salts such as sodium chloride to the mixture to cause thesame to separate into layers, one consisting essentially of -soap andthe other including Water, glycerin and added salt. The two layers areseparated by decantation and by thismeans glycerin liquor containinglarge amounts of salt and Water is produced. The glycerin liquors arethen evaporated to remove a large part of the water and to cause part ofthe salt to crystallize out. The partially concentrated glycerin liquorsare then concentrated by distillation to produce a high glycerincontent. During this stage the presence of large amounts of salts whichare poor heat conductors results both .n large expenditures of heat andin superheating and requires the application of high temperatures forextended periods of time, all of which causes a decomposition ofglycerin into products like acrolein, trimethylene glycol and otherdecomposition products.

In accordance With the present invention, the soap mixture is heated outof contact with the atmosphere to a temperature suiiiciently high tocause the glycerin to be evaporated under vacuum conditions and theglycerin is thereby directly separated from the soap in relatively pureform without the additionV of any salts or other materials for causingseparation of the glycerin. The soap mixture treated in accordance withthe present invention may be produced by theconventional batch processesbut may be advantageous- 1y produced in a continuous process such asdisclosed in the copending application Serial No.

119,168, led January 5, 1937, now issued as Patent No. 2,190,615 ofFebruary 13, 1940. Such continuous processes of making soap mixturesinvolve the continuous mixing of oil or fat and alkali solutions atelevated temperatures and out of contact with the atmosphere'to producesoap and glycerin. Such a soap mixture or one produced by theconventional batch process may be heated to a glycerin vaporizingtemperature and delivered into va vacuum chamber wherein the glycerin isvolatilized and removed in vapor form from the soap. The escape ofglycerin from the soap is a fu'lction of temperature, time and amount ofvacuum. It is generally necessary to heat the soap to a temperature atwhich it is liquid after the glycerin has been removed in order toeffect substantial complete volatilization of the glycerin. Sufficienttime must be pro. vided for the glycerin to separate from the soap, butsubjection of the soap and glycerin mixture to high temperatures forextended periods of time tures containing soap and glycerin.

In order to cause rapid separation of glycerin from the soap, it hasbeen found advantageous to spread the heated mixture in thin films uponsurfaces in a vacuum chamber. Preferably these surfaces are heated so asto maintain the temperature of the heated mixture.

It is, therefore, another object of the invention to provide a processof separating glycerin from soap by spreading a heated soap and glycerinmixture in thin films upon surfaces in a vacuum zone.

Another object of the invention is to separate glycerin from heated soapand glycerin mixtures in a vacuum chamber by spreading the same in` thinfilms upon heated surfaces. l

This operation is preferably accomplished by directing the heatedmixture against heated walls of a vacuum chamber by means of a nozzle orother opening.- The particles as they strike the wall form a film ofsoap which slides down the Walls. The lm is an efcient means of expos--ving a large portion of the soap mixture from which the soap can bereleased. By controlling the distance through which the soap mixturetravels down the Walls of the chamber, sufficient time can be providedfor substantially complete separation of glycerin Without substantialdamage to the soap or glycerin.

This method of evaporating glycerin from a soap mixture producesentirely different results than merely spraying the mixture of `soap andglycerin into the chamber. While the film travels down the sides of thechamber only its clean surface is in contact with the kettle atmosphere,whereas the particles of soap formed by spraying have their cleansurfaces exposed to thekettle atmosphere for only a comparatively shorttime before they fall to the bottom ofthe chamber. In sprayingoperations, mounds or heaps of soap build up on the bottom of thechamber, and this interferes with the proper volatilization of theglycerin from the soap. A much longer time l longer times. Also smallsoap particles formed by spraying are blown over or carried with thevapors and the soap in the: bottom of the chamber does not releasevolatiles smoothly but sudden explosive upheavals occur in the soap massresulting in the blowing up ,of soap particles which are entrained inthe vapors removed from the chamber.

By directing the soap against the walls of the chamber la downwardflowing film of soap is produced which loses volatiles as it travelsdown the sides of the chamber. There is no building up of soap particlesor superposed soap films resulting in explosive liberation of vapors.The carrying over of soap particles with the vapors is thereby greatlyminimized and the volatilization of glycerin takes place smoothly andrapidly.

A particularly effective way of discharging the mixture of glycerin soapagainst the wall of the vacuum chamber is to use revolving nozzles. Therevolving nozzle makes efiicient use of the kettle as the entirecircumferencel of the surface of the walls is coated with a thindownwardly flowing film of soap from which the glycerin is rapidly andsmoothly released. Stationary discharge nozzles which direct the mixtureagainst the walls of the chamber are also contemplated by the presentinvention, although only that surface of the kettle within the fan-likespray is utilized in the volatiliaztion of glycerin from the soap.

It is, therefore, an object of the invention to provide a process andapparatus in which the entire circumference of the walls of a vacuumchamber is employed for glycerin volatilization.

Other advantages and objects of the invention will appear in thefollowing description of preferred embodiments of invention described inconnection with the attached drawings, of which:

Figure 1 isa schematic view of a complete apparatus for recoveringsubstantially pure glycerin from soap;

Figure 2 is a fragmentary view in section of an evaporating chambershowing one type of revolving nozzle;

Figure 3 is a horizontal section taken on the line 3-3 of Figure 2;

Figure 4 is a fragmentary sectional view of the bearing arrangement ofthe nozzle of Figures 2 and 3;

Figure 5 is a view similar to Figure 2, showing a modified form ofrevolving nozzle; and

Figure 6 is a horizontal cross-section taken on the line 6-6 of Figure5.

Referring more particularly tothe drawings, in Figure 1, I0 indicates asource of supply of soap mixture which may be a conventional soap kettleprovided with an agitator II driven from any suitable source of powerthrough a pulley I2.

As indicated before, any other suitable source of soap mixture may beemployed, for example, a continuous saponication process disclosed inapplication Serial No. 119,168 now issued as Patent No. 2,190,615 ofFebruary 13, 1940, referred toabove. The soap mixture may be pumped by ahigh pressure pump I3 through a heating device shown as a coil I4 andinto an evaporating chamber I5. The temperature of the mixture is raisedin the heating coil I4 by any suitable means such as a burner I6 forgaseous or liquid fuel, to a temperature sufllciently high to causeglycerin to be evaporated in the evaporating chamber I5.

While only one coil I4 is shown, two or more such' coils in -which themixture is brought tosuccessively higher temperatures in series maysometimes be desirable along with additional pumps between the coils toforce the mixture therethrough. The temperature reached in coil or coilsI4 will depend upon the type of soap being processed but will usuallyfall between temperatures of 450 and 620 F. vThese temperatures areusually above the decomposition point of the materials from which thesoap'was made, and -care must be taken that substantially completesaponiflcation is obtained before subjecting the mixture to such hightemperatures. In Figure 1, stationary nozzles I1 are shown and thesoapmixture is discharged against the wall I8 of the evaporating chamberI5. The soap mixture flows down the wall I8 in a thin film such that theglycerin vapors are rapidly and substantially completely liberated.Relatively high superatmospheric pressures are usually employed in thecoll I4 to prevent too great vaporization therein.. 'I'hus pressuresranging from 50 to 1000 pounds imposedby the pump I3 and maintained byrestricted orifices in the nozzles I1, by a valve I9' in the pipeleading from the coil I4 to the evaporating chamber I5 or by making thepipe of coil I4 sufficiently small, may be employed in the coil I4depending upon the amount of vaporization desired therein. By employingpressures in the upper portion of the range above given, the mixture maybe maintained substantially all in liquid phase in the coil I4, but ingeneral it has been found preferable to provide at least partialvaporization of glycerin in the coil I4in order to increase the amountof heat which may be imparted to the mixture therein.

As any vaporization of glycerin in the evaporating chamber I5 tends tocool the film of mixture upon the walls I8, it is generally necessary tosupply additional heat to the mixture in the evaporating chamber I5.This can be conveniently done by enclosing .the evaporating chamberwithin arheating jacket 20 through which any desired heating medium suchas steam or heated mineral oil-may be circulated by means of the pipes2| and 22. Additional heat for vaporization can thereby be supplieddirectly to the film of mixture upon the wall I8 and the soap may bemaintained in liquid form after Water and glycerin vapors have beenremoved therefrom so that it will flow downwardly into the lower portionof the evaporating chamber I5. Also additional heat may be suppliedbyintroducing steam, preferably superheated to a temperature at least ashigh as that of the mixture leaving the coil I4, into the vacuumchamber, for example,'by the pipe 22.

In order to promptly remove the soap from th evaporating chamber and tocool the same, a screw conveyor 23 provided with a cooling jacket 24-can be conveniently employed. Such a device is effective to continuouslydischarge the substantially anhydroussoap from the evaporating chamberwithout breaking the vacuum and also to cool the soap below atemperature at which it would be damaged by contact with the air beforecontacting the soap with the air.

The housing 25 of the conveyor 23 forms a part of the evaporatingchamber I5 land the soap is delivered through a restricted passageformed by enlarging the end portion 26 of the conveyor so as to plug theconveyor housing against entrance of air. 'A valve 2'I may be providedin the discharge end of the conveyor housing so that the vacuum may bemaintained during starting and stopping of the apparatus when no soap ispresent in the conveyor housing 25.

The vapors are withdrawn from the evaporating chamber through a pipe 2Band may be delivered to an entrainment separator 29. It will be notedthat discharging the mixture against the walls of the chamber I5 andcausing the same to ow downwardly along the walls, provides asubstantially unimpeded path for the vapors upwardly through theevaporating chamber 28. The vapors/ are thus not required to passthrough a spray of material and entrainment is largely prevented.Entrainment separator 29 has been illustrated as including a helicalbaiile 30 formed between the casing 3| of the entrainment separator andan inner baille 32 so that the vapors passing through the separator areforced to folp low a helical path and then make an abrupt turn upwardlythrough the barile 32 to the vapor withdrawal pipe 33. Thus entrainedliquids or solids are thrown outof the vapors and are conducted back tothe evaporating chamber through the pipe 34.

`One or more condensers 35 provided with rey ceivers 36 are provided forcondensing the glycerin water vapors withdrawn from the vacuum chamberl5 either in a single condenser or in any desired fractions in severalcondensers. Ayacuum is maintained in the receivers, condensers andevaporating chamber I5 by means of a vacuum pump 31 connected to thelast receiver 36. It is desirable to maintain as high a vacuum ascommercially practicable in the evaporating and condensing system.Thus,` vacuums ranging from 26 to 29 inches of mercury have beensuccessfully employed. Condensate may be withdrawn from the receivers 36through pipes 38 by any suitable means, for example, pumps (not shown).

The structure shown inFigures 2, 3 and 4 provides rotating nozzles 39 bywhich the heated soap mixture may be distributed around the periphery ofthe wall i8 of the evaporating chamber. The soap mixture may bedelivered into the chamber with considerable velocity and by radiallyinclining the nozzles 39 as shown in Figure 3 and pivotally 4connectingthe nozzles at lll with the pipe Lll delivering the mixture into thechamber, the nozzles can be caused to revolve. A suitable rotaryconnection for the nozzle is shown in Figure 5 and may include astationary element 42 to which the pipe di is connected by means of athreaded member 33. A pipe d supporting nozzles 3S is rotatively securedto the member l2 by an anti-friction bearing including bearings 45, abearing race 56 secured to the stationary member (l2, and a bearing race6l secured to the rotary pipe 3d. A nipple 33 is secured to thestationary member l2 and extends downwardly within th'e rotary pipe d5and .a iiange i9 may be secured to the rotary pipe Srl for preventingentrance of extraneous material into the bearing races i6 and el. Bythis structure the nozzles 39 will continuously revolve in the samemanner as a reaction turbine.

In Figures 5 and 6 is shown a device in which rotation of the nozzle isproduced through external gearing so that the speed of the same may beaccurately controlled. Thus, a rotating member 58 extending through apackingv gland 5i in the wall i8 of the evaporating chamber may carryrotating nozzles 52. The shaft 50 and nozzles 52v may be rotated by abevel gear 53 secured to the shaft 56 and driven by a pinion 54. Byproviding a hollow bore in the shaft 50 and connecting the pipe 55 whichdelivers the heated material to the evaporating chamber to the shaft 50Table I Percent fatty Amount of Percent oi R... teem me glyin mentir'roduold ce1-n con Gouden' l gcerinlconp densates sates g ensates Pounds302. 75 11. 0 0. 34 373. 75 ll. 7 0.37 432. 13. 7 0. 346 248. 0 l2. 6 0.37 v 268. 10. 6 0. 19

The amount of total glycerin condensates represents all of thecondensate collected in the condenser system, and it will be noted thatthe amount of these total condensates is always much less than theamount of soap produced, in most cases being only slightly more than 50%of that amount. This is contrasted with the conventional method ofsaltingout glycerin, in which the glycerin waters or spent lyes rangefrom an amount approximately equal to the soap produced to three timesas much or more, This means that much less water must be. evaporated inthe present process to produce a concentrated crude glycerin. Also thetotal impurities in the `total glycerin condensates are much less vthan1% since there is no salt present as contrasted with the 5 to'15% ofsalt and the 1% or more of nonvolatile organic impurities present in theglycerin water from conventional glycerin separation steps. This issummarized in the following table:

Table II Combined condensates Spent lye of present process liquorsPercent glycerine 1l-l8% 3-10%. Amount of salt None 545%. Organicimpurities Fxboglyless than 0.09%- More than 1%.

As an example of the composition of the various condensates which can beobtained from a condenser system employing four condensers, thefollowing table relating to Run #l of Table I is given:

Table In Percent Percent of Pounds oi fatty matter No. of condenserglycerin 1n.

condensate including soap condensate in condensate 5. 25 81. 8 2. 48 2A.0 24. 5 0. 81 257. 0 9. o y 0. 2s 1e. 5 1. o o. o

It will be noted that a large percentage of the impurities was collectedin the rst condenser which was nearest the evaporating chamber andthatvthe other condensates are relatively pure.

Table IV I II III Percent Percent Percent Percent glycerol 56.loliJJ-vqlatile organic mattei- A comparison of such crude glycerinsfrom such conventional processes and the total 'condensate from thepresent process evaporated to approximately 80% glycerin is given in thefollowing table:

Table VV Evaporated crude glycerin Crude glycerin oi present processPercent Amount of salt 5- Ni-volatile organic mat- None 0.5-5.0%

s. o-Qo. o

In the above table, the amount of ash tabulated for the present processis from the nonvolatile organic matter, chiefly soap, as there are noinorganic salts present, while the ash for conventional evaporated crudeglycerin is from both the salt and non-volatile organic matter present.It is a comparatively simple matter to obtain substantially pure highlyconcentrated glycerin from the crude glycerin of the present process bydistillation because of the high purity of the crude glycerin, but theamount of salt and organic impurities of the evaporated crude glycerinfrom salting out processes renders the distillation thereof extremelydifficult. Large amounts of these impurities accumulate in the still.-cause local overheating of the glycerin in the still, and result inthermal decomposition thereof to produce products such as acrolein,trimethylene glycol, etc., which products are present in the condensedglycerin and are difficult to remove therefrom.

Also, the present process provides for an almost complete separation ofthe glycerinfrom the soap. Soap containing much less than 1% glycerinhas been consistently produced by the present process. The amount ofglycerin -retained in the soap, if a glycerin carrying soap is desired,may, however, be easily controlled by varying the temperature at whichthe soap mixture is introduced into the evaporating chamber, thetemperature or vacuum maintained therein,- or the length of time thesoap'remains in the evaporating chamber or any combination of theseconditions.

This application is a division of my copending application Serial No.172,644, filed November 3, 1937, now issued as Patent No. 2,195,377 ofMarch 26, 1940, Process and apparatus for recovering glycerin.

While I have described the preferred embodiments of the invention, it isunderstood that the details thereof may be varied within the scope ofthe appended claim.

,I claim:

A high speed apparatus for making soap and recovering relatively pureglycerin comprising, in combination: a heating device, means fordischarging a saponified mixture of soap and glycerin from said heatingdevice as a continuous stream, an evaporating chamber, a spraying nozzleadapted to direct said stream along the interior surface of the wall ofthe said evaporating chamber so that the same descends slowly as a lmthereby permitting suillcient time to vaporize substantially all of theglycerin therefrom without decomposition to the soap, means forwithdrawing said vaporized glycerin and condensing the same, means forintroducing superheated steam into said evaporating chamber to assist inthe removal of the glycerin vapors from said chamber and maintain thetemperature of said soap above the melting point when anhydrous, saidspraying nozzle being constructed and arranged so that the superheatedsteam and the vaporized glycerin ascend within said chamber withoutcolliding with the saponified mixture being introduced thereto wherebythe glycerin removed and cooled is substantially foreign matter.

' BENJAMIN CLAYTON.

free ofv

